the act of using knowledge and or information against someone else in order to gain advantage in an intense situation

Bill owes Greg his phone that Greg let him borrow. Bill has avoided Greg in order to not give back Greg's phone. Greg finds Bill to confront him and ask for his phone back. Bill says "Not right now, I can't". Greg then shows Bill the title to his car he is holding in his hand. Bill then says, "Ok here is your phone." Greg engaged in powerplay.

1: (sports, general) A massive attack, moving many players up on the opposing team's court.
2: (icehockey) When one team is playing with a player more than the opposing team because of penalties.
3: (politics) The threat or use of power (military, economical etc) as coercion.
4: (rpg) Hoarding xp and money. Often to the extend of ruining the gameplay for other players.

1: "By an impressive show of power play LA overran the Ny defence."
2: "The Dynamoes had 5 minutes of effective power play, but still couldnt score."
3: "Eritrea gave in to the US power play and signed the treaty."
4: "I hate that Ü83R-Paladin character, always power playing instead of helping out with the quests."

When you get someone to do something for you unknowingly, often the person initiating the powerplay is asserting dominance by assigning someone else a tedious task.

Let's say you and your friends have a buzzer to let you know when the bbq is coming. Say... Joseph is lazy and does not want to get the food, he slyly moves the buzzer over to Andrew. The buzzer goes off...

"Andrew go get the food it's ready."

Andrew proceeds to get the food and brings it to the table. Andrew unknowingly performed an irksome task for Joseph and is powerplayed.

To unrealistically overpower your character's opponent, usually in a fight, in a chat, forum, or other text based RPG, and overstepping the bounds of realism in that particular universe. This includes a physically weaker character A beating a strong B in a fight because A's writer said so, or an inexperienced character beating an experienced one at their own game when it simply couldn't happen realistically. Related to godmodding and metagaming in that they're all dick moves

Becky used her strongest magical defense shield to protect herself

Susan kicked a hole in Becky's shield with her light blast and punched Becky in the face, in an obnoxious powerplay, since Susan just started learning magic and Becky has been practicing for years